The present invention generally relates to air brakes for trailers and, more particularly, to a system for locking the air brakes of a parked trailer detached from a tractor.
Air brakes have evolved over the years in tractor and trailer applications and have thus become safer. One such type of air brake uses two pneumatic circuits in Ad order to provide compressed air to the brakes for actuating them. These brakes are spring-loaded so as to be normally in an actuation position, i.e., such that a trailer has its brakes on when no compressed air is supplied to the brakes. When the trailer is connected to a tractor, a supply air line linking the trailer to the brake system of the tractor supplies compressed air to the brakes so as to disengage them, i.e., keep them in a retracted position. The tractor driver will then actuate the brakes of the trailer via a service air line, which also connects the tractor""s brake system to the trailer. The combination of the service air with the springs of the air brakes will surpass the supply air of the supply air line to actuate the brakes of the trailer to the actuation position. The service air may then be exhausted to retract the brakes. This configuration of spring-loaded brakes with supply and service air lines provides an important safety characteristic to these air brakes: in the event of a failure to the supply air line, such as a leak therein, the brakes will be applied automatically. The connections between the tractor""s brake system and the supply and service air lines are typically made by gladhands, which are well known air line connectors. The gladhands are typically positioned on both sides of a nose box at a front end of the trailer so as to be connected to the brake system thereof. When the tractor is coupled to the trailer, the supply lines from the tractor are connected to the nose box.
The air brakes utilize air lines which may easily be connected to the air brakes of a tractor. It is, therefore, relatively simple to steal a trailer. Obviously, this presents a plurality of problems, as the trailers are frequently filled with expensive merchandise, making them an attractive prey for thieves. Furthermore, with the quantity of tractors and trailers on the roads nowadays, stolen trailers may go virtually unnoticed.
Various devices and methods have been proposed in order to disable the trailer air brakes such that trailers detached from tractors cannot be stolen. One problem is that trailers very seldom have sophisticated controls nor electrical systems and, therefore, anti-theft devices are mainly mechanical. Although most of these locking systems provide adequate theft prevention, none describes a locking system which arms automatically, i.e., locking systems must be manually armed. An automatic-arming locking system has advantages, one of which is that it does not require that a driver remember to arm the locking system, as it is done automatically. Also, time is saved in the arming of the locking system. Finally, it will prevent the use of air supplies from another system or tractor to deactivate the spring brakes so as to steal the trailer.
Therefore, it is a feature of the present invention to provide an automatic-arming locking system for trailer air brakes to prevent theft of a trailer disconnected from a tractor.
According to a broad aspect of the present invention, there is provided a locking system for trailer air brakes of the type having a supply air line with a gladhand for being connected to an air supply from a tractor for disengaging the trailer air brakes from an actuated position. The locking system comprises a valve connected to the trailer supply air line. The valve is actuatable between an open position, wherein the valve enables air conveyed in the trailer supply air line to disengage the trailer air brakes from the actuated position, and an exhaust position, wherein the valve exhausts air through an exhaust port thereof from the trailer supply air line such that the trailer air brakes remain in the actuated position. The valve moves automatically to the exhaust position when the tractor air supply is disconnected from the gladhand so as to cause the trailer air brakes to be engaged in the actuated position. A locking device has a portion being automatically displaceable to a locking position when the valve is actuated to the exhaust position so as to lock the valve in the exhaust position, and being displaceable to a disarmed position by manual disarming means for unlocking the locking device and displace the valve to the open position.
According to a further broad aspect of the present invention, there is provided a method for automatically locking air brakes of a parked trailer in an actuated position, the trailer being of the type having a supply air line with a gladhand for being connected to an air supply from a tractor for disengaging the trailer air brakes from an actuated position. The method comprises the steps of i) providing a valve having a rod automatically displaceable to an extended position when a tractor air supply is disconnected from the gladhand of the trailer, with the rod interfering with the gladhand when displaced to the extended position, and a locking device for automatically locking the rod in the extended position; ii) disconnecting the tractor air supply from the gladhand to engage the air brakes in the actuated position, and simultaneously causing the rod to automatically move to the extended position to interfere with the gladhand; and iii) locking the rod in the extended position by the locking device automatically locking the rod in the extended position, whereby the rod interferes with the gladhand such that air cannot be reconnected to the supply air line for disengaging the trailer air brakes from the actuated position thereof unless the rod is unlocked.
A method for automatically locking air brakes of a parked trailer in an actuated position, the trailer being of the type having a supply air line with a gladhand for being connected to an air supply from a tractor for disengaging the trailer air brakes from an actuated position. The method comprises the steps of i) providing a valve in the supply air line automatically displaceable to an exhaust position when a tractor air supply is disconnected from the gladhand of the trailer, and a locking device for automatically locking the valve in the exhaust position; ii) disconnecting the tractor air supply from the gladhand to engage the air brakes in the actuated position, and simultaneously causing the valve to automatically move to the exhaust position; and iii) locking the valve in the exhaust position by an automatic displacement of the locking device, such that any air supplied to the supply air line is exhausted through the valve, whereby the trailer air brakes are locked in the actuated position unless the valve is unlocked.